In the related art, the cutting inserts disclosed in Patent Documents 1 to 4 and the like are known as cutting inserts used in cut processing on a work material. Specifically, the cutting inserts disclosed in Patent Documents 1 to 4 are used in milling processing such as face milling or end milling. The cutting insert disclosed in Patent Document 4 has a cutting edge curved to be upwardly convex when viewed from the side.
Regarding the cutting inserts, as illustrated in FIG. 1, the largest impact is applied to a cutting insert 10 in a case where the angle formed by a ridge el of a cutting edge with respect to an end surface S of a work material 200 is small when the cutting insert 10 starts to cut into the work material 200 when viewed from above, that is, in a case where the entire ridge el of the cutting edge strikes the end surface S of the work material 200. When the impact applied to the cutting insert is increased, a large impact is transmitted between the cutting insert and the work material and chatter vibration is generated. Then, when the chatter vibration becomes very large, there is a risk of damaging the cutting insert or cutting tool.
In the cutting insert disclosed in Patent Document 4, the cutting edge has a convex curved shape which curves upward when viewed from the side. In such a case, the chatter vibration can be reduced because the impact applied to the cutting insert can be controlled to be smaller when the cutting insert starts to cut into the work material. However, because the total length of the cutting edge in the cutting insert disclosed in Patent Document 4 is long in comparison with a cutting insert where the cutting edge has a linear shape when viewed from the side, the contact length of the cutting edge becomes long with respect to the work material. As a result, the time during which cutting force continues to be applied to the cutting insert is also increased.
The present invention has been made in view of the above problems. An object of the present invention is to provide a cutting insert, a cutting tool, and a method for manufacturing a cutting tool and a cut workpiece, which can suppress chatter vibration and control increases in the cutting resistance when the cutting insert starts to cut into a work material.
Patent Literature 1: Japanese Unexamined Patent Application Publication No. 2006-75913A
Patent Literature 2: Japanese Unexamined Patent Application Publication No. 2006-88332A
Patent Literature 3: Japanese Unexamined Patent Application Publication (Translation of PCT Application) No. 2010-523352A
Patent Literature 4: Japanese Unexamined Patent Application Publication No. H09-225724A